Text and illustrations: Pieter den UdenPhotography: Bonsai Europe Studio

Its about eleven years since I was on thesearch for red flowering hawthorn(Crataegus oxyacantha). Most of the trees Ifound, though, were unsuitable as bonsaibecause they had a poor root base, andonly high branches on the trunk, which alsohad no movement in it not a favourablescenario. So I decided to grow themmyself, just the way I wanted

Because of my education in horticulture, I had someknowledge of the art of grafting. First of all I graft-ed with red flowering hawthorn but, later on, I graftedon other deciduous and coniferous species, too. Byexperimenting and learning from experts, I managed toimprove my technique. I will show you how I graftwith hawthorns.Grafting is to place a freshly cut part of a plant in bud(the scion) directly on to a freshly cut trunk with a rootball (rootstock). The aim is to encourage both to growtogether as a single plant. There are different methodsof grafting for deciduous trees, but the main goal isthat you have a rootstock and a matching scion. Themethod demonstrated here is the one I use for graftinghawthorn, but it can be implemented for almost anydeciduous tree.

Why graft?Grafting is used when plants grown from seed take toolong to mature, dont blossom in a reasonable time,nor grow true to type. Pine, beech, or red hawthorn isdifficult to propagate from cuttings. Some plant vari-eties simply dont have strong roots, so they are graft-ed on to stock that posseses this quality.

Natural response to a cut or woundWith grafting, we make use of the healing ability ofplants. The so-called Cambium layer helps to heal overcuts or other wounds. The Cambium is a one-cell layerthat generates new tissue to transport liquids, forgrowth in girth and is situated between the sapwood,phloem and bark layers. Transportation of water andnutritious salts are to be found in the sapwood layer.In the phloem layer the nutritives produced by theleaves circulate downwards. When you graft, both thescion and the rootstock will develop cells that have acorky texture, called Callus. Under the influence of theCambium layer the callus cells will grow over the bareface of the wound.

Grafting red hawthorn

Getting up early toask the nursery-man if I can cutsome shoots formy scions from hishawthorn stock

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(1) The rootstock ofthe hawthorn(Crataegus monogy-na) is selectedaccording to thick-ness and root base.The roots are prunedand the trunk is cutvery short, so thatyou can place thescion very close tothe root base. As aresult, when thebuds sprout they willdevelop brancheslow on the trunk

(2) Here I cut theroot stock

(3) Here I try to fitthe rootstock withthe scion of aCrataegus PaulsScarlet

(4) I carefully matchthe cut areas of therootstock and scion

Grafting technique is shownbelow in the drawing

Long maturedshoots ofCrataegus oxya-cantha PaulsScarlet, which willbe grafted on therootstock ofCrataegus monog-yna. Note the budsat the side of theshoots

The healing is a gradual process, the rate being directlyrelated to the health and growth of the tree. You canonly graft plants that are genetically of the samespecies. A pine grafted on to hawthorn is impossible.

Grafting toolsA Grafting knife: with a good grip.You should have avery sharp knife because if the wound is untidy orjagged the graft will take longer to hold. Some materialto bind the graft to the stock cloth, raffia or elastic.I use elasticised string because this is easy to workwith. Another advantage is that it adjusts to the thick-ening of the trunk and wont bite into the bark.

Wax for graftingI normally use wax which needs to be heated on astove. The wax should start to melt, but not allowedto boil or become hotter than 80 degrees Celsiusbecause it starts to burn. You can easily apply the waxon to the graft with a brush. Wax stops the graft fromdrying out and protects it from infections. If your graftis kept in a polytunnel or cold frame, you neednt applythe wax because the higher humidity can cause thegraft to rot beneath the wax.

Correct rootstockThe rootstock should be free of viruses and fungi. Tryto obtain trees with trunks of the same diameter andwhich are true to type. The root system should begood and spreading. For this I use the hawthornspecies Crataegus monogyna or laevigata.

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The graft is held tightly to the rootstock while elasticised tape iswrapped around the point where both ends meet. The end shouldcross over your finger; then you slip the end under your finger-tipand pull your finger away. After which the tape will fit tightlyaround the graft.

At work in the polytunnel, grafts aretreated with wax and planted in acrate with Torf. Later these will beplanted in the open field.

This is a graft with six buds, too many for such a small shoot and itis possible that it will dry out. Shorten it to three buds and you willhave more success, and with a better chance of the trunk fattening (Above left) Here you have two examples of grafting methods: thetop example shows that when the rootstock is thicker than thescion it is grafted on the side . The lower example shows the resultof the method I use (Above right) wax is being applied to the wound

Obtaining fresh scionsScions are obtained from matured 1-year-old shoots.With Prunus or hawthorn these shoots are easilyrecognised because they are long and grow straightup. I always ask at nurseries if I can remove suchshoots and make sure that I only select those that arefree of virus and pests and that they have no otherdamage. The cut shoots should have a between 3 to 5buds. Directly after taking the shoots they should bewrapped in a plastic bag and stored in the fridge, cool-ing them to between 0.5 and 3 degrees Celsius. Theshoots for the scion will remain fresh for about 14days, after which they can no longer be used for grafting.

When to graft?For successful grafting, it is necessary that the plantscells are active round the spot where you are going tograft. To promote cell activity you need a temperatureof at least 13 degC, but it shouldnt be too hot either the maximum temperature to encourage cell activityis 32 degC. The best growing temperature is 20 degC.I start to graft hawthorn in early spring say aroundthe end of February or the beginning of March. Theadvantage of this timing is that the plant is still dormant.

AftercareAfter grafting you can place the plants in a cold frameor polytunnel in a growing bed of Torf (sifted pinebark). With plastic, protect them from severe frosts orthe occasional sunny day, but remove it when it is notneeded to let the plants air and prevent them frombudding. Check regularly for fungi or pest attacks. InApril when temperatures rise, you can plant the stockin open ground 20 centimetres apart, so that all budsreceive enough sun to promote equal budding on eachtrunk. After one growing season all side branches should bepruned back to 5 cm to promote a dense branch struc-ture. The grafts can be lifted during the second yearand the root ball pruned to promote a fine root struc-ture. Even the branches are reduced at this time. Toobtain a trunk with a better taper, the top is reducedto a side branch from which the trunk will grow on. Ifyou prefer, you can choose to grow the graft in atraining pot, but from my experience I can tell you thatnothing beats the results you get from the open field.The trunk will thicken less in a pot.

Pests and diseases All hawthorn are vulnerable to mildew, gall, midge andscale insects. Start to spray with pesticides before thebuds sprout, to prevent growth slowing down.

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You can buy the wax in the spe-cialised garden sundries outletswhere nurseries do their shopping

Elasticised bindings to hold thescion and rootstock together

This forest planting consists ofhawthorn (Crataegus oxyacan-tha Pauls Scarlet) which Igrafted entirely myself. The for-est is only a couple of yearsold, but the trees were trainedin the field for more than fiveyears. The grafts are hard toidentify (detail left)

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Not just a knife, this is a special graftingknife with a curved blade

The wax is being melted on an electrichotplate; its important not to let it boil